Content uploaded by Luis Felipe Verdeja
Author content
All content in this area was uploaded by Luis Felipe Verdeja on Sep 10, 2014
Content may be subject to copyright.
Content uploaded by Luis Felipe Verdeja
Author content
All content in this area was uploaded by Luis Felipe Verdeja on Jun 07, 2014
Content may be subject to copyright.
Monitoring and control of hearth refractory
wear to improve blast furnace operation
R. M. Duarte
1
, I. Ruiz-Bustinza*
1
, D. Carrascal
2
, L. F. Verdeja
3
, J. Mocho
´
n
1
and
A. Cores
1
Refractory wear and skull growth on the hearth walls and the bottom of the blast furnace have
been researched. A series of thermocouples were installed in the hearth, and the temperature
measurements were recorded in a structured query language every minute. A heat transfer model
was used to study the temperature evolution and hearth wear profile using a commercial software
package (MATLAB version 5.0) based on computational fluid dynamics. The location of the
1150uC isotherm in the hearth lining has been calculated. An online monitoring tool was used to
analyse the temperature distribution in the hearth and offers, to the plant operators, periodic
information on the refractory state. Electromotive force (EMF) probes were installed in the hearth
to estimate the variations in the liquid level in the hearth and to determine the thermal state (TS)
evolution. Good correlation is seen between EMF and TS, and the EMF amplitudes in the different
tapholes follow and even precede the local TS.
Keywords: Blast furnace, Hearth, Hot metal tapping, Hearth profile, Refractory wear, Electromotive force, Online monitoring
Introduction
Much research has focused on blast furnace hearth, for
instance, analysing refractory damage in order to help
furnace operators take protective measures in the
identified hearth wear area to improve furnace safety
and prolong its service life.
1–5
Damage in the hearth area
is difficult to repair, and it is therefore vital to monitor
the hearth refractory condition so that its failure can be
prevented and operating practices can be adjusted to
maximise hearth life.
The hearth is monitored by an array of thermocouples
to estimate the location of the 1150uC isotherm; the
location of this isotherm can be used to indicate if the
refractory is severely eroded or if there is a lot of skull on
the hearth walls. There are a number of modelling
techniques for determining the location of the 1150uC
isotherm: (i) two-dimensional modelling,
6
(ii) two-
dimensional heat transfer modelling
7,8
and (iii) two-
dimensional heat transfer, fluid flow, mass transfer
modelling.
9,10
A severely eroded lining may indicate
that a relining should be scheduled to avoid breakout.
To be able to take the correct measures against erosion
or against the opposite situation that is a skulled hearth,
it is important to know the thermal state (TS) of the
hearth.
11
In the present work, an online monitoring tool was
used to analyse the temperature distribution in the
hearth. Measurements from 200 thermocouples were
recorded in a structured query language database every
minute. This tool offers periodic information on the
refractory state to the plant operator. A heat transfer
model based on the thermocouple readings in the
refractory can be used to consider the present state of
the hearth, i.e. if it is severely eroded or if there are
considerable amounts of skull. Electromotive force
(EMF) probes have been installed in the blast furnace
and are used by operators as an indicator of hot metal
temperature and to estimate variations in the liquid level
in the hearth. The EMF signals were analysed to
determine the hearth TS evolution and to find any
possible correlation that could improve the information
available. Different temperature profiles have been
calculated, including 1150uC. The position of the
1150uC isotherm inside the hearth throughout the
furnace campaign will be a manifestation of the level
of wear that hearth presents in different areas.
The results of the present research carried out should
be useful to increase the stability, security and campaign
life of the blast furnace.
Heat transfer model
This model was used to study the temperature evolution
and the hearth wear profile. It analyses the thermal
conditions of cooling at the hearth bottom and evaluates
three types of refractory design: refractory bricks,
carbon blocks and mixed design. The temperature
distribution calculation is based on the location of the
1150uC isotherm in the hearth lining, which provides the
1
National Centre for Metallurgical Research, CENIM (CSIC), Avda.
Gregorio del Amo, 8, Madrid 28040, Spain
2
ArcelorMittal Corporacio´n Sideru´rgica, Apdo. 570, Gijo´n 33280, Spain
3
Sid-Met-Mat Research Group, Universidad d e Oviedo, ETSIMO,
Independencia 13, Oviedo 33004, Spain
*Corresponding author, email irbustinza@cenim.csic.es
350
ß
2013 Institute of Materials, Minerals and Mining
Published by Maney on behalf of the Institute
Received 10 February 2012; accepted 4 May 2012
DOI 10.1179/1743281212Y.0000000045
Ironmaking and Steelmaking 2013 VOL 40 NO 5
best fit between the temperature distribution calculated
by the model and that measured by thermocouples
inside the lining.
Usually, depending on the refractory design and
composition, hearth models may be grouped into three
types:
(i) traditional refractory design constructed prefer-
entially with a silicon–alumina refractory mate-
rial. Until the 1960s, hearths were built mainly in
this way, and the furnace (hearth) campaign life
rarely exceeded 2 years
(ii) thermal design (from the mid 1960s) in which a
carbonaceous anthracite, anthracite–graphite or
graphite material is only used. Simultaneously
cooling of hearth walls and bottom technologies
(water or air) began. These technologies in-
creased significantly the campaigns to around
7 years; however, heat losses were greater, im-
pacting negatively on the consumption of coke
(iii) ceramic cup design in which oxide or nitride
ceramics are in contact with the hot metal and
anthracite–graphite is in contact with the hearth
walls and bottom. This design was proposed at
the end of the last century and consisted of
oxidic/nitrided (oxides and nitrides of alumi-
nium) in contact with hot metal, with carbonac-
eous (anthracite with greater or lesser proportion
of graphite) in contact with the furnace walls
(steel plate construction). With this solution, the
campaign life is extended to .15 years and with
heat losses lower than with the thermal solution.
The present work takes into account research carried
out on the mathematical simulation of hot metal flow
and heat transfer in the hearth. This research is based on
the free space formation in the hearth using a cold two-
dimensional model,
12
the erosion analysis by numerical
computation
13
and a model to simulate the effect of a
coke free gutter full of low porosity material on the
temperature distribution and rate of tapping.
14,15
A heat transfer model has been designed using an
axisymmetric finite element method to calculate the
temperature profile inside the hearth refractory in order
to estimate the maximum wear. Using a commercial
software package, PDE toolbox of MATLAB (version
5?0), CSIC/CENIM has developed a model based on
computational fluid dynamics. The effect of the hot
metal temperature and cooling conditions has been
researched using a moving boundary approach at the
hot metal/refractory interface, in which, depending on
the temperature distribution, the hot metal thermal
properties sequentially replace the refractory thermal
properties.
The basis of the mathematical formulation is the
balance between mass and heat conservation. The
following suppositions may be established. (i) The
deadman is floating. (ii) Heat is not generated in the
refractory, and therefore, this thermal source may be
disregarded. (iii) The problem may be simplified to two
dimensions as there will be small irregularities in the
geometry, material properties and limit conditions in the
angular direction, and so angular thermal conductivity
may also be disregarded. (iv) A steady state is
considered, because changes on the hot side and limit
conditions on the cold side are slow, and so the
temperature distribution in the hearth is almost static.
Using the variational principle and making a finite
element discretisation, the heat balance equations can be
reduced to the following form
K½| T
fg
~ Q
fg
(1)
and calculated as follows
K½~
X
i
2p
ðð
B½
T
D½
:
B½
:
rdrdzz2p
ð
Cc
h N
S
T
N
S
:
rdC
C
0
@
1
A
(2)
Q½~
X
i
2p
:
ð
Cq
q
:
N
S
:
rdC
q
z2p
ð
Cc
hT
a
:
N
S
T
:
rdC
C
0
B
@
1
C
A
(3)
and B and D (conductivity) matrices can be represented
as follows
B½~
L
Lr
L
Lz
T
N½;D½~
K
r
0
0K
z
where [K] is the global heat conduction matrix, {T}is
the global nodal point temperature vector, {Q} is the
global heat flux vector, [B] is the conductive matrix, [D]
is the conductive matrix, c is the diffusivity (cm
2
s
21
), r,
z are cylindrical coordinates, h is the overall heat
transfer coefficient (W m
22
K
21
), [N] is the element
interpolation (shape) function matrix, [N
s
] is the element
surface interpolation function matrix, q* is the heat flux
(W m
22
) and T
a
is the fluid temperature (hot metal or
cooling fluid) (uC).
In this work, a standard two-dimensional four-noded
isoparametric quadrilateral element has been used. Since
the thermal conductivity values and consequently the
heat conduction matrix [K] coefficients are functions of
temperature, the global equation (1) is solved iteratively
at each load step using a frontal solution method until
convergence is established.
In order to evaluate the model, some data and input
properties, in conjunction with the temperatures mea-
sured in the thermocouples placed in the hearth lining,
were necessary as follows:
(i) hearth: internal and external diameter and
height
(ii) molten liquid iron: production rate, average
temperature, density, laminar viscosity, thermal
conductivity, calorific capacity, thermal volu-
metric expansion coefficient, molten liquid iron
thickness (from hearth bottom), liquid height
above top of taphole and carbon diffusion
coefficient for a melt (cast iron) with a certain %
C
(iii) slag: height
(iv) hearth lining: thermal conductivity, calorific
capacity and density
(v) coke bed: particle diameter and density
(vi) other data: hearth wall and bottom cooling
water temperature, conduction heat transfer
coefficient in hearth side wall and bottom (as
a function of the temperature measured by
thermocouples) and convection heat transfer
coefficient of cooling water.
To evaluate this model, the temperature profile and
maximum hearth wear have been calculated using the
ArcelorMittal blast furnace B design, as mentioned
above (see Table 1). Furthermore, different hearth
refractory materials could be studied including their
(2)
(3)
Duarte et al. Monitoring and control of hearth refractory wear
Ironmaking and Steelmaking 2013
VOL 40 NO 5 351
thermal conductivity values as a temperature function
for each material.
Online supervision of hearth refractory
state using advisory tool
For a long blast furnace (BF) lifetime, it is important to
form a protective skull on the hearth side walls and
bottom surfaces by means of an appropriate cooling
system for these zones in order to avoid their over-
heating. An online monitoring tool is used to analyse the
temperature distribution in the hearth and, conse-
quently, the heat transfer between the lining materials
and cooling system in order to establish the state of the
refractory.
BF-B has .200 thermocouples fitted inside its
refractory. Measurements from all the thermocouples
are recorded in a structured query language database
every minute. In parallel, the most significant process
data are also recorded in the other sets of the same
database. Figure 1 shows a cross-section of the thermo-
couple distribution. There are three horizontal layers in
the hearth bottom and two vertical layers in the hearth
wall at different levels. Figure 2 shows the current
situation and the various thermocouple installed levels.
The database also has information on the water
temperature and cooling system temperatures, and so
it is possible to monitor the evolution of thermal losses.
The advisory tool offers to the plant operator periodic
information on the refractory state using a thermo-
couple temperature graphic display in different positions
and levels of the lining and calculating their evolution
compared to the initial temperature values measured
after the BF-B revamping period (start of 2003). The
initial temperature data were selected by analysing the
measured relationships between thermocouples from the
present campaign start (end of January 2003).
With these online displays, it is possible to analyse
when and where scaling appears and the progress of
refractory wear on the hearth walls and bottom. An
algorithm calculates the refractory thickness by compar-
ing the selected data values with the values from the
same thermocouples at the start date, according to the
heat transfer model used.
Figures 3 and 4 show the evolution of temperatures
comparing the initial data values (February 26, 2003),
midterm values (May 11, 2006) and 4 year values
(December 29, 2006). Figure 3a shows the temperature
variations at level 2L, over the taphole, indicating that
the temperatures basically decrease close to the taphole
zone, probably due to the scaffolds produced during
tapping. Figure 3b shows the temperature variations at
level L, below the taphole, indicating that the tempera-
tures rise close to the taphole area, due to the turbulence
produced during tapping, with the consequent occur-
rence of refractory wear in this zone. Figure 4 shows the
circumferential distribution of hearth temperatures at
levels 2K and K, below the taphole levels. The tem-
perature behaviour here is similar to that of level L.
During the temperature measurements, abnormal
thermal evolution has been detected in the readings
from thermocouples close to the hot wall of the pad.
Many of the thermocouples in the layers closest to the
hot side, especially those near the centre of the hearth,
showed erratic behaviour over time, with very low tem-
peratures compared to the readings given by thermo-
couples closer to the cold side. This behaviour can be
seen in Fig. 5, where the ‘red’ thermocouple is closer to
1 Thermocouples in BF-B hearth
Table 1 ArcelorMittal blast furnace B (BF-B) characteristics
Parameters and operation conditions of ArcelorMittal BF-B
Value Unit
Hearth Internal diameter 11
.
3m
External diameter 13
.
5m
Liquid height 3
.
7–5 m
Refractory wall thickness 1
.
1m
Tapholes Tilt angle 10 u
Diameter 45 mm
Liquid Iron Melt Production rate 6500 t/day
Density 6
.
66 t m
23
Slag Height 3
.
7–6 m
Coke bed Particle diameter 4
.
3mm
Other data Cooling water temperature
at sidewall and bottom hearth
45 uC
Heat transfer coefficient by
conduction at sidewall and
bottom hearth (as a function
of the temperature measured
by thermocouples)
Sidewall:
100uC–6 W uCm
21
800uC–11 W uCm
21
Bottom:
100uC–5 W uCm
21
800uC–10 W uCm
21
Heat transfer coefficient by
convection (h) of cooling water
1500 W m
22
uC
21
Duarte et al. Monitoring and control of hearth refractory wear
352 Ironmaking and Steelmaking 2013 VOL 40 NO 5
the hot side. From the thermocouple inspection, it is
deduced that the most likely reason for this mismatch is
the presence of moisture inside the thermocouple casing:
the protective corrosion cover allows cooling water to
wet the internal insulation by porosity and diffusion.
This problem leads to the dismissal of all pad
temperature readings from the affected thermocouples
and underlines the interest of using parallel monitoring
2 Thermocouple distribution along side walls and bottom of ArcelorMittal BF-B (TH15north, TH25centre, TH35south taphole)
3 a hearth temperature variations at level 2L; b hearth temperature variations at level L (midterm values at 330
u
inconsis-
tent due to problems with thermocouples)
Duarte et al. Monitoring and control of hearth refractory wear
Ironmaking and Steelmaking 2013
VOL 40 NO 5 353
systems in future hearth design, such as heat flux metres,
which also allow the abnormal measurement detection
and the estimation of thermal conductivities.
Analysis of wear profiles
The revamping of blast furnace A (BF-A), at the end of
2004 (the end of its campaign life was in October 1997),
allowed hearth wear profile analysis at the end of the
campaign. The main aspects on the lining profile wear
were as follows:
(i) the ceramic wall had disappeared above the
bottom block level
(ii) on most of the wall surfaces, including areas close to
the taphole, the remaining carbon coating can be
described as follows, starting from the hot side:
N
thick layer (,500 mm) of damaged carbon
blocks, heavily infiltrated with metal (Fig. 6)
N
thick brittle layer, often so damaged that it
turns to dust
N
after an even more brittle transitory material
(thickness, 20–50 mm), an undamaged carbon
layer of thickness varying between 120 and
500 mm
N
finally, the rammed layer against the shell,
whose appearance is normal.
The severest wear was located at the G2/G3 interface,
i.e. at the level of the upper face of the upper ceramic
bottom layer (Fig. 7). This is a normal position for the
elephant foot. The lining located over the tapholes was
also an area that suffered strong erosion (Figs. 8 and 9).
The increase in wear here originated by the faster flow of
metal and slag above the taphole area. As a conse-
quence, the skull protection is less efficient. The brittle
layer closest to the shell can be divided into three parts:
on the sound carbon side, a very damaged layer of
50 mm thickness converted into dust, followed by plates
of infiltrated material with a high iron content (100 mm
4 a hearth temperature variations at level 2K; b hearth temperature variations at level K
5 Abnormal behaviour of pad thermocouples. Dashed
line thermocouple is closer to hot face and continuous
line to cold face. The period of time is 10 months
6 Aspect of brittle layer at level of G2, close to taphole
no. 2 (brittle layer is located between ‘G’ and ‘2’)
Duarte et al. Monitoring and control of hearth refractory wear
354 Ironmaking and Steelmaking 2013 VOL 40 NO 5
thickness) and finally a second layer of 50 mm thickness
also converted into dust. After this comes the thickest
part (500 mm) considered as the damaged hot side of the
carbon blocks, with some remaining adhered skulls.
The carbon block samples have been obtained by core
drilling through the entire lining below taphole nos. 1
and no. 2 at the level of the elephant foot area in the
hearth bottom (Fig. 10). Factors that can accelerate
wear include a lack of protective skulls, which are
washed out when the metal flow is fast (high productiv-
ity), the carbon conductivity is low and the hot metal
infiltration is strong. As the lining hot side reaches the
7 Wear profile (elephant’s foot)
8 Wear profile above tapholes
9 Above taphole no. 1 (north). The erosion of the carbon
blocks is greater
Duarte et al. Monitoring and control of hearth refractory wear
Ironmaking and Steelmaking 2013
VOL 40 NO 5 355
highest temperatures in this area, it is recommended to
use carbon blocks with a constant linear change,
maintaining low values established to limit stresses on
the hot side of the lining. Alkali infiltration seems to
cause more disintegration than zinc infiltration. The
highest alkali contents have been found in samples
converted into dust. It has also been observed in drilled
nucleus samples that outside the brittle layer area, liquid
hot metal infiltration is more intense than alkali and zinc
penetration, which was not expected.
Thermal state and thermal profile
analysis
Heavy wear was observed in the taphole area during the
revamping of BF-A, to an extent of 1 or 2 m in width,
produced by the faster hot liquid flow. Greater attention
must be paid to this area in future designs as the current
protection is not sufficient to assure good resistance
against erosion. The results provided by the software
developed by CSIC/CENIM to estimate the evolution of
wear have been compared by ArcelorMittal with the
aforementioned observations. Although the calculations
were performed with a data set from BF-B, both
furnaces have the same design and similar campaigns.
According to CSIC/CENIM, higher temperatures are
detected close to and below the tapholes than in other
sections of the hearth, which indicates higher wear in
these areas. This seems to be in accordance with the
wear found during revamping. Moreover, the model
points to higher temperatures in the elephant foot area,
which is consistent with the observations.
On the other hand, the high wear found above the
tapholes is not clear from the model results, which must
be due to the presence of scaffolds or the lack of
measurements from thermocouples sufficiently close to
the wear zone. Successive statistical and correlation
analyses have been carried out with the information
provided by the thermocouples from the hearth and
different furnace operating parameters, taking into
account factors such as distribution of the nozzle pipe
openings, horizontal and vertical thermocouple levels
and the active taphole.
Thermal state and EMF
In a qualitative approach to determine the hearth TS,
the data generally analysed by the operator are the hot
metal temperature and the silicon content.
16
Following
this criterion, it is possible to define work areas for BF
operation according to the hearth state (cold, hot or
good) and to check this tendency, taking actions to
correct any abnormal behaviour. As the temperature
and the silicon percentage are intensive variables, the
(%Si–T) couple defines a hearth energy function known
as the TS
TS~TS (T, %Si, T
obj
, %Si
obj
) (4)
where T
obj
is the target hot metal temperature set by the
operator, and %Si
obj
5%Si resulting from correlation
with the temperature.
The area definitions are shown in Fig. 11. Level 0 is
defined as the objective and corresponds to the target
temperature and silicon resulting from the correlation.
Electromotive force probes have been installed in BF-
B to estimate variations in the liquid level of the hearth,
and a strong correlation between the EMF measures and
the iron level has been observed.
17
The measurement of
the EMF between two sensors that are welded to the
furnace shell at two levels (one used as a common
voltage reference) is a method to determine the amount
of liquid in the hearth. The voltage value depends on the
relation between slag and hot metal. It has been detected
10 Core C2 sampled by drilling at level z5500 below taphole no. 2. From the left to the right: 50 mm rammed mass,
125 mm of unaffected material, 45 mm close to the brittle layer and with carbon dust, 70z80 mm of strongly metal
infiltrated carbon and 220 mm of transition to the slag/lime/metal skull, then only skull
11 Thermal status graph
Duarte et al. Monitoring and control of hearth refractory wear
356 Ironmaking and Steelmaking 2013 VOL 40 NO 5
that the EMF signal shows a good correlation with the
casting sequence; generally, the signal has a minimum at
the end of casting.
The signals were analysed to determine the hearth
thermal evolution and to find any possible correlation
that could improve the information available. When
different tapping sequences are observed, the general
short term evolution of the EMF signals is seen to be
directly related with the tapping sequence and the liquid
level in the hearth, and is also especially well correlated
with the TS, so that the highest EMF amplitudes mean
higher TS values. This could be explained if the
mechanism that produces EMF was better known.
Recent studies
18
indicate that chemical reactions at the
interface between the hot metal and slag are responsible
for the difference in voltage. Thus, a higher TS may
mean higher reactivity with an increase in EMF
amplitudes. The conclusion obtained from this simple
analysis is that the tendency of the hearth TS is also
reflected in the evolution of EMF. Figure 12 shows the
correlation between the north probe average EMF of
different melts and the TS. The direct relationship is
clear.
The following analyses yielded new results. The local
evolution of each of the measured EMF amplitudes has
been verified, comparing their evolution with the hot
metal temperature obtained during tapping in the
corresponding taphole where the probe was installed.
It has been seen that the relative difference in the EMF
values measured by the probes placed in different
tapholes is closely related with the difference in the hot
metal temperature measured in those tapholes.
Figure 13 shows a sequence of melts, where the EMF
amplitudes measured in the north and south tapholes
have crossing points: when the EMF values of the north
taphole are higher than in the south taphole, the
measured temperatures are also higher, and the gap
between the tapholes is high. When the reverse occurs,
the gap decreases. In the end, the EMF values in the
north probe are once again higher, and the gap tends to
increase. This type of evolution is always similar;
qualitatively, it can be said that the EMF amplitudes
not only provide information about the filling level of
the hearth and the overall TS but also seem to indicate
the local TS in the different sectors of the BF where they
have been installed.
Thermal profiles
The information provided by the EMF measurement is
used by the BF-A and BF-B operators as an indicator of
the hot metal temperature and the TS evolution. In fact,
13 Typical EMF evolution during different taps. Hot metal temperature gap behaviour when the EMF values in different
sectors of the hearth cross.
12 Correlation north probe EMF versus thermal status
Duarte et al. Monitoring and control of hearth refractory wear
Ironmaking and Steelmaking 2013
VOL 40 NO 5 357
the operators’ experience with EMF signals is that the
amplitude not only follows but actually precedes the
thermal conditions of the next tap. The operators
habitually use this information as another tool to
improve tapping practice. A study has also been carried
out in relation with deviations that occur in thermo-
couples located at the same height and radial position
but at different angular positions.
19
For this purpose,
erosion profiles have been calculated for selected angular
positions by defining the cold side temperature limit
conditions and using the data provided by the pairs of
thermocouples located in these positions (Fig. 14).
The limits of some conditions have been defined in the
mathematical model to obtain the expected results. The
first thing was to study heat transfer in the hearth
refractory of BF-A. The metal/refractory interfaces in
the side walls and bottom block have been fixed at the
constant hot metal temperature of 1450uC. Convective
limit conditions have been specified for the surface of the
outer walls and the bottom block using average
temperature data recorded in the plant, and approx-
imate convective heat transfer coefficients have been
taken for the cooling water and air. Furthermore, the
surface of the refractory at the top and in the centre of
the hearth has been considered to be adiabatic. After
this, different temperature profiles have been calculated,
including 1150uC, using different water and air tem-
peratures. Convective coefficients have also been used to
determine how cooling conditions affect the temperature
profiles (Table 2). It has been seen that changes in the
1150uC isotherm for cold side limit conditions are
negligible. However, when the 1150uC isotherm is
calculated for different hot metal temperatures (e.g.
1400 and 1500uC), significant effects have been seen on
the hot metal/refractory interfaces (Fig. 15). The beha-
viour of the 1150uC isotherm is studied by changing the
temperature of the hot metal/refractory interface and its
effect on refractory wear.
Conclusions
On the basis of the results obtained about the wear
mechanism of blast furnace hearth, the following
conclusions may be drawn.
1. For the carbon blocks in the hearth under ceramic
cup model/design to avoid the elephant foot profile, the
following is recommended: higher block thermal con-
ductivity but with good resistance to corrosion by hot
metal, a low permanent linear change (of the refractory
material as a consequence of the work of this material at
high temperature) and a high level of microporosity.
2. Resistance to attack by alkalis and zinc is an
important parameter for carbon quality. In its evaluation,
the phenomena of both cracking and expansion must be
taken into account. Blast furnace operators are interested
in limiting the alkali and zinc content in the burden
materials.
15 Effect of hot metal temperature at refractory interface
on 1150
u
C position in BF-B hearth
Table 2 Cooling conditions
Case A Case B
Water temperature T
w
/uC30 15
Fluid temperature T
a
/uC35 20
Overall water heat transfer
coefficient h
w
/W m
22
K
21
300 3000
Overall air heat transfer
coefficient h
a
/W m
22
K
21
10 100
14 Hot metal temperature effect at refractory interface on 1150
u
C isotherm position using EMF
Duarte et al. Monitoring and control of hearth refractory wear
358 Ironmaking and Steelmaking 2013 VOL 40 NO 5
3. Differences in the TS at each taphole are indicative
of asymmetric hearth conditions, which, in terms of long
term evolution, may lead to differences in wear.
4. There is a direct correlation between the hearth TS
and the evolution of EMF in the taphole area.
5. The information reported in the present work on
the analysis of hearth refractory state has improved the
understanding of the wear mechanism and will be useful
to the operators of blast furnaces to allow future
improvements in hearth design.
References
1. ‘Technical study into the means of prolonging blast furnace
campaign life’, Final report ECSC research contract no. 7210-ZZ/
570, EUR 17247, 1995.
2. ‘Effects of hearth liquid level upon blast furnace operation’, Final
report ECSC research contract no. 7210-AA/133, EUR 19347,
2000.
3. ‘An in-depth study into prolonging blast furnace campaign life’,
Final report ECSC research contract no. 7210-ZZ/586, EUR
19970, 2001.
4. ‘Wear of blast furnace hearth’, Final report ECSC research
contract no. 7210-PR/006, EUR 20109, 2002.
5. ‘Enhanced blast furnace operation and service life by improved
monitoring and control of the hearth and uniformity’, Final report
ECSC research contract no. RFSR-CT-2003-00013, EUR 23455,
2008.
6. A. Rex, P. Zulli, P. Plat, W. Tanzil, T. Skimmings and T. Jelenich:
ISS Ironmaking Conf. Proc., 1993, 52, 603–609.
7. G. Leprince, J. M. Steiler, D. Sert and J. M. Libralesso: ISS
Ironmaking Conf. Proc., 1993, 52, 123–132.
8. J. Torrkulla, J. Bra¨nnbacka, H. Saxe´n and M. Waller: ISIJ Int.,
2002, 42, 504–511.
9. T. Inada , K. Takatani, M. Miyaha ra, S. Wakabayasi, T.
Yamamoto, A. Kassai and K. Takata: ISS Ironmaking Conf.
Proc., 1999, 58, 633–639.
10. V. Panjkovic, J. Truelove and P. Zulli: Ironmaking Steelmaking,
2002, 29, 390–400.
11. J. Torrkulla, J. Bra¨ nnbacka and H. Saxe´n: ISS Ironmaking Conf.
Proc., 2000, 59, 481–487.
12. K. Shibata, Y. Kimura, M. Shimizu and S. Inaba: ISIJ Int., 1990,
30, 208–215.
13. A. Preuer, J. Winter and H. Hiebler: Steel Res., 1992, 63, 139–
146.
14. M. J. Venturini, J. P. Bolsigner, J. Iezzi and D. Sert: Proc. 2nd Int.
Cong. on ‘Science and technology of ironmaking’ and Proc. 57th
Ironmaking Conf., Toronto, Ont, Canada, March 1998, Iron and
Steel Society. 615–622.
15. M. J. Venturini, M. Nogues, J. M. Steiler, D. Lao and A. Dufour:
Proc. 3rd European Ironmaki ng Cong., Gent, Belgium, September
1996, 263–269.
16. N. S. Hur, B. R. Cho, J. S. Choi and K. S. Heor: Proc. 2nd Int.
Cong. on ‘Science and technology of ironmaking’ and Proc. 57th
Ironmaking Conf., Toronto, Ont, Canada, March 1998, Iron and
Steel Society. 581–585.
17. H. Saxe´n and J. Bra¨nnbacka: Scand. J. Metall., 2005, 34, 116–121.
18. ‘Optimization of tapping strategy by advanced assessment of the
liquid level in the heart of the blast furnace’, Contract no. 7219-
AA/142, EUR 19482, 2000.
19. M. Swart ling, S. Sundelin , A. Tilliander and P. Jo¨ nsson:
Ironmaking Steelmaking, 2010, 37, 21–26.
Duarte et al. Monitoring and control of hearth refractory wear
Ironmaking and Steelmaking 2013
VOL 40 NO 5 359
